A micro-sized nuclear reactor is currently being developed at Chalk River Labs in Ontario, Canada,
and it could be ready to start replacing diesel power generation with clean electricity in remote
mines and off-grid communities within 5 years. Most nuclear power plants today are giant
stations producing hundreds of megawatts or even gigawatts of electricity. But lately small
modular nuclear reactors seem to be gaining traction. SMRs would generate less electricity
but could be mass produced in factories at lower cost than their traditional counterparts,
and many governments around the world have plans to start constructing these designs.
A sub-class of these SMRs are very small, or Micro Modular Reactors, which would be small
enough to power off-grid communities, mines, or factories. One such reactor has been designed by
the Ultra Safe Nuclear Corporation, and the first one will be built in Chalk River, Ontario by 2026.
The USNC design would produce 5MW of electricity and consists of two parts – the actual nuclear
reactor, and the adjacent power plant. Let’s take a look at the nuclear reactor first.
Most nuclear reactors operating today use pressurized water as a coolant, but the USNC
design would use helium gas as a coolant instead. Helium was chosen because its an inert gas,
meaning it can’t react chemically with the nuclear fuel or any other component of the reactor. It’s
also easy to measure and control the helium pressure in the reactor. Another unique safety
feature of the MMR is its fuel. The USNC design will use Fully Ceramic Micro encapsulated fuel,
which allows the fuel to contain its own radioactive material during operations
or in the unlikely event of an accident. Since the fuel contains its own radioactive material,
this also means that the helium coolant is not contaminated with fission products
unlike the pressurized water coolant in traditional reactors. To make this fuel,
you start with TRISO fuel particles. TRISO stands for TRi-structural ISOtropic particle fuel,
which is a small kernel of uranium fuel encased in three layers of carbon- and ceramic-based
materials. The TRISO particles are very robust and can’t melt – they were originally developed
in the 60s for use in gas-cooled reactors. The TRISO particles would then be encased in
a dense silicon carbide matrix to make pellets – it’s this matrix that makes it “fully ceramic
micro encapsulated.” The pellets would be stacked and placed into a graphite core, which
acts as the moderator for the reactor and also has channels for the helium coolant and control rods.
The reactor core is designed to have a high heat capacity but a low power density, resulting in
slow and predictable temperature changes. The design is also passively safe, because the
reactor has no need for outside electricity or services to operate and has no need for active
cooling. In the unlikely event of an accident, heat is passively dissipated to the surroundings,
preventing the reactor from melting down without the need for any operator intervention.
The reactor core is deigned to operate for twenty years. After the twenty years are up, the reactor
can either be decommissioned, or the core can be replaced and the reactor can continue operating.
Ok, so we’ve taken a look at the nuclear reactor itself, but the adjacent power
plant also has some unique features compared to traditional reactors. In traditional reactors,
the water coolant is generally pumped through a heat exchanger to generate steam which then spins
a turbine and generates electricity. But in the USNC design, instead of using the helium
coolant to directory boil water to create steam, the gas will heat up molten salt which would be
kept in the adjacent plant. The molten salt would store the heat created by the nuclear reaction
and could be used to boil water and generate electricity on demand – an important feature
that would allow the MMR to adjust its power output, something traditional reactors can’t do.
In a large, national-scale power grid, traditional nuclear reactors are used to generate baseload
power, meaning the minimum amount of power that is required at all hours. This is because nuclear
reactors aren’t very good at turning on and off quickly or adjusting their power output,
they work best when they’re operating at full capacity nearly 100% of the time.
Additional electricity demanded during peak hours is generated with another method that
can be turned on and off more easily – for example, natural gas. But in an off-grid
mine or community where the MMR is potentially the only source of power, it would have to be able to
adjust its output to meet demand, which is why the molten salt storage system is used in the design.
But the heat stored in the molten salt doesn’t have to be used to generate
electricity – industrial operations using the MMR could instead use it for process heat.
But could a very small nuclear reactor really replace diesel generators? After all, the
nuclear industry does have a reputation for being very expensive – could the MMR realistically be
economically competitive with diesel generation? Well, diesel power generation isn’t very cheap,
so the nuclear reactors don’t have to be super low cost to be competitive. Diesel generators do
have low up front costs compared to other methods of power generation, but fuelling them is quite
costly. While most Canadians pay between $0.07 and $0.17 per kWh, diesel generally costs around $1.30
per kWh. Furthermore, because of the remoteness of many mines and the need for reliable power,
mining operations usually have twice the needed diesel generation capacity to ensure their
access to electricity. Ontario Power Generation, Canadian Nuclear Laboratories, and Mirarco Mining
Innovation conducted a feasibility study on using very small modular reactors to power remote mines.
They found that electricity costs could be reduced if the reactors were used to provide baseload
power, or around 90% of the mine’s electricity demand, with diesel generators being used to
supply peaking power. Besides reducing electricity costs in the mines, this would also cut the mining
operations’ CO2 emissions by 85%. However, the very first MMR being built in Chalk River,
which is meant to be complete by 2026, will not be economically competitive with diesel – it’s moreso
meant to be a demonstration of the technology. There are plans to construct larger, 10 MW units
that will be economically competitive with diesel generation after the first 5MW unit is complete.
Its not just remote mines that could benefit from these Micro Modular Reactors. Remote,
off-grid communities could also benefit. In 2018, there were 292 off-grid communities in Canada,
most of which are indigenous. These communities mostly use diesel generators for electricity,
and the high cost of diesel means the government has to subsidize their fuel. And the high costs
aren’t the only downside – there’s also a high risk of diesel spills which has other
negative environmental and health effects. And many of the diesel generators used are old and
unreliable, meaning these communities face many power outages and load restrictions.
The unreliable electricity and the load restrictions make it difficult
to build new homes and businesses. More reliable and lower cost electricity could
reduce the government subsidies required and help grow the local economies of these communities,
and MMRs could be a source of that electricity. Of course, nuclear power isn’t the only potential
solution to these problems. The government is also making investments in local wind,
solar, hydro, and biomass electricity generation for off-grid communities in Canada.
MMRs might be a great way to make electricity generation in off-grid mines and communities more
environmentally friendly, but just as the first MMR will be under construction, a significantly
larger nuclear power plant, the Pickering Nuclear Generating Station, will be shutting down. This
will leave a 3 GW hole in Canada’s electricity production that will likely be filled with
fossil fuels. Check out my other video to learn more about the history of Pickering,
why it’s shutting down, and how we could make it’s closure less painful for the environment.